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From: Arnd Bergmann on 1 Jun 2010 17:00
Calling wait_event_interruptible implicitly
releases the BKL when it sleeps, but we need
to do this explcitly when we have converted
it to a mutex.

Signed-off-by: Arnd Bergmann <arnd(a)arndb.de>
---
drivers/char/cyclades.c | 2 +-
drivers/char/istallion.c | 12 ++++++++----
drivers/char/n_r3964.c | 2 +-
drivers/char/tty_port.c | 2 +-
drivers/char/vt_ioctl.c | 2 +-
drivers/serial/crisv10.c | 4 ++--
include/linux/tty.h | 42 ++++++++++++++++++++++++++++++++++++++++++
7 files changed, 56 insertions(+), 10 deletions(-)

diff --git a/drivers/char/cyclades.c b/drivers/char/cyclades.c
index 51acfe3..27aad94 100644
--- a/drivers/char/cyclades.c
+++ b/drivers/char/cyclades.c
@@ -1607,7 +1607,7 @@ static int cy_open(struct tty_struct *tty, struct file *filp)
* If the port is the middle of closing, bail out now
*/
if (tty_hung_up_p(filp) || (info->port.flags & ASYNC_CLOSING)) {
- wait_event_interruptible(info->port.close_wait,
+ wait_event_interruptible_tty(info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
return (info->port.flags & ASYNC_HUP_NOTIFY) ? -EAGAIN: -ERESTARTSYS;
}
diff --git a/drivers/char/istallion.c b/drivers/char/istallion.c
index 5e9a81d..be28391 100644
--- a/drivers/char/istallion.c
+++ b/drivers/char/istallion.c
@@ -954,7 +954,7 @@ static int stli_rawopen(struct stlibrd *brdp, struct stliport *portp, unsigned l
* order of opens and closes may not be preserved across shared
* memory, so we must wait until it is complete.
*/
- wait_event_interruptible(portp->raw_wait,
+ wait_event_interruptible_tty(portp->raw_wait,
!test_bit(ST_CLOSING, &portp->state));
if (signal_pending(current)) {
return -ERESTARTSYS;
@@ -989,7 +989,7 @@ static int stli_rawopen(struct stlibrd *brdp, struct stliport *portp, unsigned l
set_bit(ST_OPENING, &portp->state);
spin_unlock_irqrestore(&brd_lock, flags);

- wait_event_interruptible(portp->raw_wait,
+ wait_event_interruptible_tty(portp->raw_wait,
!test_bit(ST_OPENING, &portp->state));
if (signal_pending(current))
rc = -ERESTARTSYS;
@@ -1020,7 +1020,7 @@ static int stli_rawclose(struct stlibrd *brdp, struct stliport *portp, unsigned
* occurs on this port.
*/
if (wait) {
- wait_event_interruptible(portp->raw_wait,
+ wait_event_interruptible_tty(portp->raw_wait,
!test_bit(ST_CLOSING, &portp->state));
if (signal_pending(current)) {
return -ERESTARTSYS;
@@ -1052,7 +1052,7 @@ static int stli_rawclose(struct stlibrd *brdp, struct stliport *portp, unsigned
* to come back.
*/
rc = 0;
- wait_event_interruptible(portp->raw_wait,
+ wait_event_interruptible_tty(portp->raw_wait,
!test_bit(ST_CLOSING, &portp->state));
if (signal_pending(current))
rc = -ERESTARTSYS;
@@ -1073,6 +1073,10 @@ static int stli_rawclose(struct stlibrd *brdp, struct stliport *portp, unsigned

static int stli_cmdwait(struct stlibrd *brdp, struct stliport *portp, unsigned long cmd, void *arg, int size, int copyback)
{
+ /*
+ * no need for wait_event_tty because clearing ST_CMDING cannot block
+ * on BTM
+ */
wait_event_interruptible(portp->raw_wait,
!test_bit(ST_CMDING, &portp->state));
if (signal_pending(current))
diff --git a/drivers/char/n_r3964.c b/drivers/char/n_r3964.c
index f4bd259..a98290d 100644
--- a/drivers/char/n_r3964.c
+++ b/drivers/char/n_r3964.c
@@ -1079,7 +1079,7 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,
goto unlock;
}
/* block until there is a message: */
- wait_event_interruptible(pInfo->read_wait,
+ wait_event_interruptible_tty(pInfo->read_wait,
(pMsg = remove_msg(pInfo, pClient)));
}

diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index a3bd1d0..35eb304 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -231,7 +231,7 @@ int tty_port_block_til_ready(struct tty_port *port,

/* block if port is in the process of being closed */
if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING) {
- wait_event_interruptible(port->close_wait,
+ wait_event_interruptible_tty(port->close_wait,
!(port->flags & ASYNC_CLOSING));
if (port->flags & ASYNC_HUP_NOTIFY)
return -EAGAIN;
diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c
index cc07fab..c56c4f3 100644
--- a/drivers/char/vt_ioctl.c
+++ b/drivers/char/vt_ioctl.c
@@ -133,7 +133,7 @@ static void vt_event_wait(struct vt_event_wait *vw)
list_add(&vw->list, &vt_events);
spin_unlock_irqrestore(&vt_event_lock, flags);
/* Wait for it to pass */
- wait_event_interruptible(vt_event_waitqueue, vw->done);
+ wait_event_interruptible_tty(vt_event_waitqueue, vw->done);
/* Dequeue it */
spin_lock_irqsave(&vt_event_lock, flags);
list_del(&vw->list);
diff --git a/drivers/serial/crisv10.c b/drivers/serial/crisv10.c
index d11d898..e6a1cb7 100644
--- a/drivers/serial/crisv10.c
+++ b/drivers/serial/crisv10.c
@@ -3981,7 +3981,7 @@ block_til_ready(struct tty_struct *tty, struct file * filp,
*/
if (tty_hung_up_p(filp) ||
(info->flags & ASYNC_CLOSING)) {
- wait_event_interruptible(info->close_wait,
+ wait_event_interruptible_tty(info->close_wait,
!(info->flags & ASYNC_CLOSING));
#ifdef SERIAL_DO_RESTART
if (info->flags & ASYNC_HUP_NOTIFY)
@@ -4139,7 +4139,7 @@ rs_open(struct tty_struct *tty, struct file * filp)
*/
if (tty_hung_up_p(filp) ||
(info->flags & ASYNC_CLOSING)) {
- wait_event_interruptible(info->close_wait,
+ wait_event_interruptible_tty(info->close_wait,
!(info->flags & ASYNC_CLOSING));
#ifdef SERIAL_DO_RESTART
return ((info->flags & ASYNC_HUP_NOTIFY) ?
diff --git a/include/linux/tty.h b/include/linux/tty.h
index faf0bcd..18a7955 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -603,5 +603,47 @@ static inline void tty_unlock(void) __releases(kernel_lock)
}
#define tty_locked() (kernel_locked())

+/*
+ * wait_event_interruptible_tty -- wait for a condition with the tty lock held
+ *
+ * The condition we are waiting for might take a long time to
+ * become true, or might depend on another thread taking the
+ * BTM. In either case, we need to drop the BTM to guarantee
+ * forward progress. This is a leftover from the conversion
+ * from the BKL and should eventually get removed as the BTM
+ * falls out of use.
+ *
+ * Do not use in new code.
+ */
+#define wait_event_interruptible_tty(wq, condition) \
+({ \
+ int __ret = 0; \
+ if (!(condition)) { \
+ __wait_event_interruptible_tty(wq, condition, __ret); \
+ } \
+ __ret; \
+})
+
+#define __wait_event_interruptible_tty(wq, condition, ret) \
+do { \
+ DEFINE_WAIT(__wait); \
+ \
+ for (;;) { \
+ prepare_to_wait(&wq, &__wait, TASK_INTERRUPTIBLE); \
+ if (condition) \
+ break; \
+ if (!signal_pending(current)) { \
+ tty_unlock(); \
+ schedule(); \
+ tty_lock(); \
+ continue; \
+ } \
+ ret = -ERESTARTSYS; \
+ break; \
+ } \
+ finish_wait(&wq, &__wait); \
+} while (0)
+
+
#endif /* __KERNEL__ */
#endif
--
1.7.0.4

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Prev: [PATCH 04/31] isicom: kill off the BKL
Next: [PATCH] NOMMU: Add '[stack]' label to /proc/pid/maps output